The invention relates to a procedure for the production preferably of food foams from flowable and pumpable mediums, as for instance sugar/whole eggs mixtures, egg white solutions or cream products which may be used for baked goods, biscuits and confections. The procedure is applicable in discontinuous units; it is, however, especially suitable for the use in continuous lines in the baking and confectionery industry, for instance for the production of physically aerated baked and confectionery goods as well as foamed formed confections.
The procedures for the production of food foams may be classified as follows,
discontinuous procedures PA1 continuous procedures, with gas being blown under pressure into the medium PA1 continuous procedures with gas being aspirated according to the principle of the water jet pump or the injector by changing the speed of the medium to be foamed.
In the discontinuous procedures for foam production, the well-known beating and mixing machines of different technical design are used. According to these procedures and with these machines, a volume increase up to 500 p.c. is obtained, e.g. in whole eggs/sugar mixtures. These foams are characterized by a good stability.
The discontinuous foaming procedure, however, makes it difficult to use in modern flow systems.
For a continuous procedure, a permanent delivery of medium to the beating machine must be assured, in order to operate at zero pressure and according to the "overflow" principle (Zehle, G. u.a. "Possibilities for plant rationalization-Experiences with the automated cake line", Backer u. Konditor 34 (1980) p. 201).
The continuous feeding of medium to the bowl and the horizontal and vertical turbulence during beating produces a partial mixture of foam and medium, before the whipping process has been finished, thus resulting in foams with small volume yield and stability.
The use of chemical whipping agents is unavoidable. Further continuously operating foaming units are pressure beaters ("Production methods of foamy sponges", Zucker- und Suss warenwirtschaft 30 (1977) 12, p. 448). In this case, foaming is produced by the introduction of gas, e.g. air, with compressors into the medium which also has been pressurized by pumps. Special mixing or dispersing devices with separate drive assure a fine dispersion of the air. Thus the production of foam according to the pressure beater procedure requires not only mechanical work for dispersing the gas within the medium, but also further work for producing the gas pressure. Considerable additional power consumption is required; for instance gas pressures of 0.19 to 0.98 N/mm.sup.2 are necessary for the production of food foams. Application of this principle in the food industry implies that the pressure gas, e.g. air, is in a perfect sanitary condition, i.e. the air produced by compressors must be free from foreign admixtures, e.g. of oily nature. Therefore it is necessary to deoil and clean the air by filters being arranged following the compressor, thus further increasing the number of apparatus elements required for this procedure.
Further continuous units are characterized by the aerating gas being aspirated according to the principle of the water jet pump or the injector, i.e. by changing the speed of the medium to be foamed. Specially designed fluid flow installation then is required.
The prevailing disadvantage of this physical kind of gas introduction is the proportion between the medium to be foamed and the gas being only 60:40 at most. Food foams are predominantly produced from viscous mediums which have only poor suction qualities, i.e. the amount of gas or air drawn in is very limited in these continuous procedures, thus reducing the yield of foam (Clauss, J. u.a. "Production of curd cream mixtures with continuous cream foaming", Lebensmittelindustrie 27 (1980) p. 69; DE-OS 2312573).
The principle described here is used for the production of whipped cream, as an example. An air valve is built in the inlet pipe of a rotary pump or gear pump narrowed by a special nozzle. Air is introduced by aspiration in the flow of the medium to be foamed; then the mixture medium/air is foamed in a narrow-spaced homogenizer (DD-WP 64879; DE-OS 2202324).
The volume increase obtained with this procedure is 150 p.c. This continuous procedure is favorable as to the equipment; it is, however, only limited in use as to foam yield and foam stability, because the underpressures obtained with the flow process permit a maximum volume increase also for very liquid mediums only of 300 p.c., even in the face of using special stops and nozzles for elevating the speed difference of the medium.
The disadvantages of the known procedures for the production of food foams are caused on the one hand by the insufficient under-pressure conditions of procedures based on the injection principle, so that only a limited amount of air may be aspirated; on the other hand, in pressure beater machines the aerating gas must be pressurized in a separate installation and then incorporated into the medium to be foamed in special flow devices. That means high energy consumption and a number of units.